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[scopehal] azonenberg pushed 1 commit to master [+0/-0/±2] https://git.io/JJ8Q3
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[scopehal] azonenberg 946ef1b - Fixed several bugs in de-embedding and angle interpolation
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[scopehal] azonenberg pushed 1 commit to master [+0/-0/±1] https://git.io/JJ8Ql
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[scopehal] azonenberg f0a5a3a - Still some issues with the very beginning of de-embedded waveforms. Truncate until we figure out what's causing that.
<azonenberg>
it's a giant pile of my lossiest cables all connected end to end
<azonenberg>
Lol
<azonenberg>
And the theory of operation is super simple
<azonenberg>
You convert the waveform from time to frequency domain
<azonenberg>
Rotate each complex point, backwards, by the S-parameter phase of the channel
<azonenberg>
Divide each complex point by the S-parameter gain of the channel
<azonenberg>
then convert back to time domain
<Kliment>
and where are you getting those parameters from?
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<azonenberg>
Kliment: VNA measurement of the spaghetti
<azonenberg>
The typical intended use case of this is when you have either field solver simulation or VNA measurements of a test fixture, cable, probe, etc
<azonenberg>
and you want to remove that from your measurements and focus on what the signal looked like at the DUT itself
<azonenberg>
for example at the 4 GHz bandwidth limit of my new scope, even my fancy Mini-Circuits "18 GHz" cables have 1.18 dB of insertion loss
<azonenberg>
You don't care about what the signal looks like at the scope, you want to know what it looked like coming INTO the cable
<Kliment>
Yeah makes perfect sense
<Kliment>
I just got my first VNA and I'll actually be using this
<Kliment>
but not for high speed signals, just antenna tuning in this case
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[scopehal-apps] pepijndevos commented on issue #146: glscopeclient hangs on Rigol MSO5000 - https://git.io/JJ40C
<pepijndevos>
This Rigol drive continues to prove hilariously broken
<azonenberg>
on a 1 GHz scope, it will be even more impressive with a higher bw scope i think
<miek>
i did, very cool
<azonenberg>
i'm gonna try running 1000base-X through that channels on my 4 GHz scope when it comes in on weds and probably film a youtube demo
<_whitenotifier-b>
[scopehal-apps] pepijndevos commented on issue #146: glscopeclient hangs on Rigol MSO5000 - https://git.io/JJ4El
<miek>
i wonder whether it would make any sense to apply to limits of a scope itself too? like my scope's got a ~300MHz LPF before the ADC, but it rolls off pretty slowly and i can still measure a signal way up above 450MHz as long as it's not really weak
<pepijndevos>
azonenberg, ^^^ ReadRawData probably needs an API change to work reliably with Rigol.
<azonenberg>
pepijndevos: File a separate ticket against scopehal for this
<azonenberg>
there's a few other pending API changes that need to happen
<pepijndevos>
alright
<azonenberg>
Great work on the debug so far though
<_whitenotifier-b>
[scopehal] pepijndevos opened issue #185: Expose actual number of bytes transferred in ReadRawData and possibly other commands - https://git.io/JJ4uf
<Degi>
My 70 MHz rigol can measure like 200 MHz lol
<azonenberg>
Degi: i imagine there's a fair bit of attenuation?
<Degi>
yes
<Degi>
I should upgrade it to 350 MHz sometimes... Probably when the warranty runs out
<miek>
wait, you haven't upgraded it yet? i thought that was the whole reason to get an mso5000 :p
<Degi>
Hm yes
<Degi>
Was too lazy for that, apparently since a firmware update you cant just ssh into the scope
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<azonenberg>
bvernoux: o/
<bvernoux>
hello
<azonenberg>
bvernoux: so i'm starting to try and do more advanced SI work with scopehal
<azonenberg>
Degi: because the cable has nonzero propagation delay
<Degi>
Does it correct for the phase shift in the able
<Degi>
Nice
<bvernoux>
so you apply a s2p reference to do the de-embedding ?
<azonenberg>
Yes. This is a full s-parameter model from VNA-ing the cable
<azonenberg>
bvernoux: correct
<bvernoux>
ha great
<bvernoux>
like on VNA ;)
<azonenberg>
I plan to support forward transforms soon as well
<bvernoux>
very good things
<azonenberg>
so you can model what a signal looks like through an arbitrary channel
<azonenberg>
the latest item on my list is to try and build something that simulates a PRBS, or an arbitrary waveform coming from a VCD simulation, through an IBIS buffer
<bvernoux>
and add also VNA display ;)
<azonenberg>
and generates an ideal view of what your waveform would look like in the time domain right at the chip pad
<bvernoux>
do you have seen latest Rigol Scope/VNA ?
<azonenberg>
After that, then I can apply a S2P for an arbitrary channel
<bvernoux>
the amazing things is the package QFN68 or QFN40
<bvernoux>
and of course the Built-in super high-speed USB3.0 control and transceiver (built-in PHY), support USB3.0 Host/Device mode, OTG function, support USB3.0 HUB
<bvernoux>
even Hub ;)
<bvernoux>
also HSPI is amazing
<bvernoux>
with builtin SerDes @1.25Gbps ...
<bvernoux>
the HSPI => the fastest transfer speed is about 3.8Gbps
<azonenberg>
Reading up on transmission line math is making me remember just how much calculus i've forgotten :P
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